1. Field of the Invention
The present invention relates to a video processing apparatus which can generate displayable video data from a video signal which has predetermined resolution among video signals which are identical in contents but different from one another in resolution, and a method for controlling the video processing apparatus.
2. Description of the Related Art
Conventional analog broadcasting has handled mainly videos of Standard Definition (SD) resolution. In current digital broadcasting, however, videos are broadcast with High Definition (HD) resolution based on a high-compression video coding technique in many cases. Thus, in the case of broadcasting contents generated using conventional equipment of SD resolution or past contents of SD resolution, interpolation processing is performed to increase the number of pixels, and a video having only apparent resolution converted into HD resolution may have been distributed. It is assumed that the video thus generated with no substantial resolution is referred to as a pseudo-resolution video. On the other hand, a video which is not processed to improve apparent resolution is referred to as an original resolution video.
There is known a method for determining whether a received video is a pseudo-resolution video by analyzing its spatial frequency. A video captured or generated with HD resolution includes more high frequency components than a video obtained by converting a video of SD resolution into HD resolution in a pseudo manner. Thus, for example, if a spatial frequency does not have a value equal to or more than a specific threshold value, the received video can be determined to be a pseudo-resolution video.
Japanese Patent Application Laid-Open No. 2005-328150 discusses a technique for acquiring a high quality video of HD resolution by down-converting a pseudo-resolution video into a video of SD resolution, and subsequently performing image quality enhancement processing and resolution conversion. In the technique discussed in the above reference, the pseudo-resolution video which does not have substantial resolution needs to be down-converted again. However, as described above, the pseudo-resolution video includes almost no high frequency component as compared with an original pseudo-resolution video equal in resolution to the pseudo-resolution video. More specifically, by using the pseudo-resolution video disadvantageous in image quality as compared with the original resolution video, the video is down-converted again to lower resolution. In consequence, image quality deterioration occurs in the technique discussed in the above reference.
H.246/Scalable Video Coding (SVC) that is a new video coding standard is a result of extending H.264/Advanced Video Coding (AVC) so as to multiplex a plurality of different resolutions on one stream data. A video can be decoded with desired resolution by extracting a part of the stream data.
A video is captured by equipment that can perform photographing with arbitrary original resolution at least. For example, in the case of equipment that can perform photographing with HD resolution, a video of HD resolution becomes an original resolution video. Thus, in broadcasting of videos distributed using the H.264/SVC, a video of one resolution among the videos of several resolutions is an original resolution video. A video having resolution other than the original resolution is a pseudo-resolution video generated from the original resolution video or a down-converted video.
Thus, among pieces of data coded by the H/264/SVC, an original resolution video is decoded to perform image quality enhancement processing and resolution conversion into display resolution. This processing can prevent image quality deterioration that occurs during re-down-conversion of the pseudo-resolution video converted in resolution in a pseudo manner in the conventional technology.
However, in the above described pseudo-resolution video determination method of the conventional technology, certain videos are erroneously detected. For example, in the case of a video such as a cartoon which includes many flat portions and smooth edges, a spatial frequency is originally low, and hence it is difficult to determine whether a video signal is a pseudo-resolution video signal.